From even a cursory examination of the available prior art, it is readily apparent that it has long been known to provide devices operable for sensing the level of fluid in a confined chamber. There are many reasons why it is desirable to be able to sense the level of fluid. For example, in some instances it is desirable to ascertain what the level of fluid is in order to prevent an overfilling of the confined chamber, i.e., container with fluid. Other times, it is desired to maintain essentially a constant level of fluid in a chamber. Finally, there are some applications wherein it is desired to provide a fluid level sensing means which is operable to ensure that the level of the fluid does not fall below a predetermined level. A reference to the prior art further reveals that a proliferation of different types of fluid level sensing devices have been provided heretofore. One method of categorizing these prior art forms of fluid level sensing devices is according to the manner in which the sensing is accomplished, namely, mechanically, electrically, etc. More recently, with the advent of the development of new technologies, some efforts have been made to attempt to adopt these technologies for use in devices capable of performing fluid level sensing. By way of illustration of the latter, attempts have been made to combine optics with light producing means to provide a light-sensitive device operable for sensing the level of fluid in a chamber by means of light.
With further reference to the latter type of device, a number of different forms thereof are known in the prior art. This is exemplified by the following illustrations. For example, in U.S. Pat. No. 2,984,148 there is disclosed a measuring apparatus which operates to determine the level of fluid in a chamber by measuring the amount of light energy that is absorbed as light is passed through a tubular column which is positioned in the chamber. A liquid level indicator utilizing fiberoptics and prisms forms the subject matter of U.S. Pat. No. 3,120,125. In accordance with the teachings of the latter patent, when the base surface of the prism is exposed to the air, the light rays are reflected into the sensing fiberoptics to indicate the fluid level. U.S. Pat. No. 3,192,392 shows a third type of light-sensitive fluid level sensing detector wherein a rod is provided which is capable of carrying light rays disposed within the container. The aforesaid rod has a series of notches or grooves about its circumference so that light rays will pass when the liquid level is high enough to avoid an air interface and will be reflected from the air interface when the liquid level drops therebelow. These reflected rays are sensed by a photoelectric probe located adjacent the calibrated grooves. In U.S. Pat. No. 3,384,885 there is depicted a multiple liquid reservoir level indicator which employs the end of a fiberoptic tube as a prism whereby if the liquid level in any reservoir is sufficiently low the light is reflected back through the tube in that reservoir and into another branch of the optical fiber circuit to visual indicator means. The final form of light-sensing device which will be referenced herein by way of illustration is that which forms the subject matter of U.S. Pat. No. 3,458,705. The latter patent is directed to a flow control apparatus wherein there is employed a central tube which acts as the light conductor and which has a prism surface at the end disposed adjacent to the sensing photoelectric cell.
The light-sensing means operable as fluid level sensor devices which have been referred to in the preceding paragraph are intended to merely exemplify some of the various forms thereof which have been provided heretodate by the prior art. Notwithstanding the fact that such a wide variety of such devices have been known heretofore, the performance of the latter when placed in actual use has not proven to be entirely satisfactory. More specifically, it has been shown that a need exists to provide a fluid level sensing mechanism which is capable of being employed in a system wherein a slurry has been mechanically spatulated under vacuum and a controlled dispensing of this slurry takes place under air pressure. The employment in such a system of a fluid level sensing mechanism is necessary because the escape of compressed air through the metering tube after the supply of slurry has been exhausted would produce a disastrous effect. Namely, the high velocity of compressed air would, in the event the slurry was being dispensed into cylindrical ring open at one end and containing one or more fragile wax patterns, which is a common form of application in which such a system is utilized, deform or destroy the latter, incorporate air bubbles in the slurry and cause excessive splashing thereof. Moreover, a need has existed to provide such a fluid level sensing mechanism which in addition is compatible with a system wherein a mixing paddle or agitator is used. whereby the fluid level sensing function can still be performed notwithstanding the fact that a member is being rotated through the chamber within which the fluid whose level is to be sensed is located.
Accordingly, it is an object of the present invention to provide a novel and improved fluid level sensing mechanism which is capable of being employed in conjunction with a variety of different types of process equipment utilized for dispensing or otherwise processing various fluids including liquids, slurries and powders for purposes of performing a fluid level sensing function.
It is another object of the present invention to provide such a fluid level sensing mechanism wherein light sensing means are utilized for purposes of sensing the level of the fluid.
A further object of the present invention is to provide such a fluid level sensing mechanism wherein the light-sensing means thereof includes a fiberoptic bundle which cooperates with an external light source and photoelectric means to indicate fluid level within a confined chamber.
A still further object of the present invention is to provide such a fluid level sensing mechanism which is particularly suited for use in a system wherein a slurry has been mechanically spatulated under vacuum and a controlled dispensing of this slurry takes place under air pressure.
Yet another object of the present invention is to provide such a fluid level sensing mechanism which is compatible for use in a system wherein a mixing paddle or agitator is used in that the fluid level sensing function is capable of being performed notwithstanding the fact that a member is being moved within the chamber in which the fluid whose level is to be sensed is located.
Yet still another object of the present invention is to provide such a fluid level sensing mechanism which is capable of accurately performing the fluid level sensing function, yet is relatively easy to employ.